Re: Extinction

[John Bois <jbois@umd5.umd.edu>]

On Fri, 24 Mar 2000, Stanley Friesen wrote:

> At 03:11 PM 3/24/00 -0500, John Bois wrote:
> >Specifically, among terrestrial vertebrates the ONLY group that
> >experienced true extinctions were the dinosaurs!...
> 
> Not strictly true, at least according to Archibald.  His analysis of the 
> Hell Creek and overlying layers shows the following:  50% extinction in 
> Multituberculates, 89% extinction in Marsupials, 70% extinction in 
> squamates, and 100% extinction in non-avian dinosaurs.

Yes, of course.  However, these extinctions are also coincident with (but
definitley not yet attributable too) placental invasion at the time.  So,
competition/predation hypotheses are very much alive for these particular
extinctions.